In order to upgrade or improve the appearance of low or undesirable quality wood panel surfaces, particularly with respect to paint adhesion or durability, such surfaces are often covered with an overlay or resin impregnated sheet of paper. The resultant panel, however, usually has a smooth, somewhat uninteresting appearance. It has therefore also been common to incorporate a texture or relief to the overlay panel surface, thereby lending a three-dimensional effect.
One method used to provide such a three-dimensional effect is the machining of grooves into the surface of the panel. However, in addition to the high costs incurred in the machining operation, the grooves formed in the panel by such machining contain areas of exposed wood which present problems of paint durability. In addition, an extensive or overall textured pattern is not provided by such machining.
Because of the shortcomings of machining, a technique whereby wood grain textures are embossed onto wood surfaces has been preferred. In this procedure, a caul having the desired texture or design and the panel sought to be embossed are placed between the platens of a hot press. The caul and panel are compressed under heat and pressure, so that the panel takes on and retains the relief impression of the caul.
Heretofore cauls made of metal, generally mild steel, aluminum or nickel, have been employed in a platen press for embossing. These cauls are generally textured or provided with the desired configuration by one of several manufacturing techniques. The most common technique involves the construction of a hardened metallic master tool, from which a number of individual cauls can be fashioned from relatively softer metals by the combined application of pressure and an acid etching agent. Another method involves the application of an etching agent to specified areas of a metallic surface, resulting in controlled removal of metal from the surface to produce a desired texture. Still another technique involves caul formation by electrochemical deposition of nickel onto a textured surface which has been coated with an electrically conductive primer. Lastly, there is a technique whereby a textured caul plate is formed by pouring molten aluminum into a suitable mold (sand casting).
It can readily be appreciated that in addition to the cost of the metal, the cost of producing a desired texture by any of the aforementioned techniques is relatively expensive. This cost of manufacturing tends to limit the number of different caul designs that a manufacturer can afford to use. This is obviously a significant limitation when one considers the number of potential designs that are available. It can also be appreciated that some of the methods by which metal cauls are produced--i.e. etching and casting--often yield a less than genuine reproduction of a wood grain or other texture. Another shortcoming attendant with the commercial metal cauls currently available is that they are somewhat heavy and can be difficult to handle, especially during installation and removal from a hot press.